JPH118589A - Fault monitoring device - Google Patents

Abstract

(57) [Summary] [Problem] Unless the status of a slave station is constantly monitored by complicated two-way communication control, a faulty slave station cannot be specified. SOLUTION: A downlink transmission line 30 and an uplink optical transmission line 4 connected between a plurality of slave stations 20 and a master station 10 for transmitting an optical signal.
This is a fault monitoring device for monitoring a fault of a slave station in an optical transmission system having 0, wherein the slave station generates a different frequency signal for each slave station by an oscillation circuit 27, and a synthesizer 28. R
The signal is superimposed on the F main signal and converted into an optical signal in the E / O 25a. This optical signal is transmitted to the master station via the upstream optical transmission path, and the master station receives the RF-superimposed optical signal in the slave station group O / E 13A and converts it into an electric signal. RF at splitter 31
The signal is demultiplexed into a main signal and a plurality of superimposed signals, each of the superimposed signals is extracted by each BPF 16, the level of the superimposed signal is detected by a level detection unit 17, and a control unit 19 is controlled based on the level result. When it is determined that there is a station fault, the fault of the slave station is notified by the alarm generator 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication network and, more particularly, to a master station, a plurality of slave stations performing two-way communication with the master station by optical signals, and an optical signal from the master station to the slave station. A multi-branch optical transmission system having a downstream optical transmission line for transmitting and an upstream optical transmission line for transmitting an optical signal from the slave station to a master station. The present invention relates to a fault monitoring device for monitoring on a station side.

[0002]

2. Description of the Related Art Conventionally, as a fault monitoring device of such a multi-branch type optical transmission system, an absolute value of a light receiving level of an optical signal received from each slave station at a master station or each slave station at a master station side is known. By constantly monitoring the amount of change in the light receiving level of the optical signal received from the base station, the presence or absence of a fault in each slave station is detected based on the monitoring result, and the occurrence of a fault in the slave station is notified based on the detection result. An LED that turns on an alarm LED has been considered.

[0003]

However, according to the above-described conventional fault monitoring apparatus, the fault of the slave station in the optical transmission system is detected by the master station based on the absolute value or the amount of change in the light receiving level. However, since optical signals from a plurality of slave stations are combined and received, the slave station involved in the failure cannot be identified from the plurality of slave stations in the optical transmission system, and the faulty slave station is identified. In such a case, it is necessary to provide a CPU and a digital transmission modulator in all of the master station and the slave station, and the status of the slave station must be constantly monitored by bidirectional communication such as polling communication by complicated communication control. There was a problem.

Further, according to the fault monitoring device which detects a fault in a slave station based on the absolute value, for example, a variation in the amount of light emitted by a light emitting element inside the slave station, a difference in installation status, a difference between slave stations, and a difference between slave stations. Even if the difference in transmission loss between the station and the master station is taken into consideration, it is extremely difficult to set the threshold level for failure detection under all conditions so that problems such as malfunctions do not occur. And there is a problem that the presence or absence of a failure in the slave station may be erroneously detected.

Further, according to the fault monitoring apparatus for detecting a fault in a slave station based on the amount of change, it is possible to detect a short-term sudden change in the received light level, but the optical signal of the slave station gradually decreases. In other words, if the received light level gradually decreases, it is not possible to deal with the detection of the amount of change for failure detection, and there is a possibility that the presence or absence of a failure in the slave station may be erroneously detected. There was a point.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to reliably detect the occurrence of a failure in a slave station and to control the state of the slave station through complicated two-way communication control. It is an object of the present invention to provide a fault monitoring device capable of specifying a faulty slave station from a plurality of slave stations in an optical transmission system without constantly monitoring the faulty slave station.

[0007]

In order to achieve the above object, a fault monitoring apparatus according to the present invention is connected to a master station, a plurality of slave stations, and is connected between the master station and the slave stations. A fault monitoring device for monitoring a fault in a slave station in a master station in an optical transmission system having an optical transmission path for optically transmitting an RF main signal therebetween, wherein the slave station is different for each slave station. An oscillating means for oscillating a frequency superimposed signal, and an RF main signal to be transmitted from a slave station and a superimposed signal by the oscillating means,
An RF combining means for generating an F-multiplexed signal; and a light-emitting element for converting the RF-multiplexed signal into an optical signal and transmitting the optical signal. The master station receives the optical signal transmitted through the optical transmission line. A light-receiving element for photoelectrically converting the optical signal; signal extraction means for extracting an RF main signal and a superimposed signal for each slave station from the RF multiplexed signal photoelectrically converted by the light-receiving element; Failure detection means for detecting the occurrence of a failure in the slave station based on the superposed signal disappearance of each slave station extracted by the extraction means, and failure notification means for reporting that a failure has occurred in each slave station, When detecting the occurrence of a failure in the slave station based on the disappearance of the superimposed signal in the failure presence / absence detection means, the failure notification means is notified to notify that a failure has occurred in the slave station corresponding to the lost superimposed signal. Control means for controlling It is intended.

Therefore, according to the fault monitoring device of the present invention,
When the master station extracts a superimposed signal from the RF multiplexed signal including the RF main signal from each slave station and detects the occurrence of a fault in the slave station based on the disappearance of the superimposed signal, the slave station corresponding to the lost superimposed signal The failure notification means informs that a failure has occurred in the slave station, so that the failure occurrence of the slave station can be reliably detected, and the state of the slave station is constantly monitored by complicated two-way communication control. Even if there is no slave station, a faulty slave station can be specified from a plurality of slave stations in the optical transmission system.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fault monitoring apparatus according to a first aspect of the present invention is connected to a master station, a plurality of slave stations, and the master station and the slave stations. An optical transmission system having an optical transmission line for optically transmitting a signal, an optical transmission system having an optical transmission line, wherein a supervision station monitors a sub station for a fault in the sub station, wherein the sub station has a superimposed signal having a different frequency for each sub station. Oscillating means for oscillating the signal, RF synthesizing means for frequency-multiplexing the RF main signal to be transmitted from the slave station and the superimposed signal by the oscillating means to generate an RF multiplex signal, and converting the RF multiplex signal into an optical signal. A light-emitting element for transmitting, the master station receives an optical signal transmitted through the optical transmission line, a light-receiving element for photoelectrically converting this optical signal, and a photoelectric conversion by the light-receiving element. From the RF multiplex signal, the RF main signal and the superimposed signal for each A signal extraction unit that outputs a signal, a failure detection unit that detects the occurrence of a failure in the slave station based on the superposed signal disappearance of each slave station extracted by the signal extraction unit, and a failure that occurs in each slave station. When the occurrence of a fault in the slave station is detected based on the disappearance of the superimposed signal by the fault notifying means for notifying that the fault has occurred, the fault presence / absence detecting means reports that a fault has occurred in the slave station corresponding to the lost superimposed signal. Control means for controlling the failure notifying means.

The optical transmission line corresponds to, for example, an optical fiber, and includes an upstream optical transmission line for transmitting an optical signal from the slave station to the master station, and a downstream optical transmission line for transmitting an optical signal from the master station to the slave station. Road.

This fault monitoring apparatus monitors a slave station fault relating to an upstream optical transmission system for optically transmitting an upstream RF main signal from a plurality of slave stations to a master station, and notifies the slave station fault. is there. Note that the slave station failure here means that an RF optical signal can be optically transmitted from the slave station to the master station, such as an upstream optical transmission line disconnection, a slave station power supply failure, or a failure of the slave station light emitting element. This is equivalent to an obstacle that disappears.

The oscillating means corresponds to an oscillating circuit for oscillating superimposed signals having different frequencies for each slave station.

The RF synthesizing means corresponds to, for example, a synthesizer for frequency-multiplexing an RF main signal and a superimposed signal by an oscillation circuit.

The light-emitting element corresponds to, for example, a laser diode, and the light-receiving element corresponds to, for example, a photodiode.

The signal extracting means extracts, for example, an RF main signal and a superimposed signal from an RF multiplexed signal, and extracts only a superimposed signal of a frequency assigned to each slave station from the extracted superimposed signal. (Hereinafter, simply referred to as BPF).

The failure detection means detects the occurrence of a failure in the slave station based on the disappearance of the superimposed signal. That is, when there is a superimposed signal, the slave station is normal and no failure has occurred. If it has disappeared, it detects that a failure has occurred in the slave station having the signal source. The failure detection means includes a level detection unit that detects the presence or absence of a superimposed signal, for example, the level of the superimposed signal, and a control unit that determines the presence or absence of a slave station failure based on the detection result.

The fault notifying means includes, for example, an alarm generator such as an alarm buzzer having various alarm sound patterns so as to specify a disabled slave station, and a display having various warning display patterns so as to specify a disabled slave station. It is equivalent to a vessel.

Therefore, according to the fault monitoring apparatus of the first aspect of the present invention, the master station extracts the superimposed signal from the RF multiplex signal including the RF main signal from each slave station, and removes the superimposed signal. When the occurrence of a slave station failure is detected on the basis of this, the failure notification means notifies the slave station corresponding to the lost superimposed signal that a failure has occurred. It is possible to implement multiple communication in the optical transmission system without always monitoring the status of the slave station with complicated two-way communication control without providing a complicated circuit and communication control means on the master station side. A child station with a disability can be specified from the child station.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the slave station receives the optical signal from the master station via the optical transmission line. Station-side light-receiving element; slave-station-side fault detecting means for detecting occurrence of a fault in a slave station and an optical transmission line based on an optical signal received by the slave-station light-receiving element; and slave-station-side fault detecting means. When the occurrence of a failure of the slave station is detected, the slave station side control means for stopping the oscillation operation of the superimposed signal by the oscillating means in the slave station or stopping the light emission of the light emitting element.

This fault monitoring device monitors a down light reception interruption related to a down light transmission system for transmitting an optical signal from a master station to a plurality of slave stations, and notifies the down light reception interruption. In addition, the down light reception interruption here is a failure that does not directly interrupt the light emission of the slave station, such as a failure of the downstream optical transmission system from the master station to the slave station, such as a failure of the downstream optical transmission path or a failure of the light receiving element on the slave station side. Is equivalent to

The slave station side fault detecting means monitors the optical signal transmitted from the master station at each slave station side, and detects the presence or absence of a slave station fault based on the result of monitoring the down light reception interruption.

When the slave station side failure detecting means detects the down light reception interruption, the slave station control means stops the oscillation operation of the superimposed signal by the oscillation means of the slave station related to the down light reception interruption. Alternatively, the light emitting operation by the light emitting element is also stopped.

Therefore, according to the fault monitoring device of the second aspect of the present invention, in addition to the effect of the fault monitoring device of the first aspect, the slave station receives a signal from the master station via the optical transmission line. A slave station-side light-receiving element for receiving an optical signal; a slave station-side fault detecting means for detecting occurrence of a fault in the slave station and the optical transmission path based on the optical signal received by the slave station-side light-receiving element; When the slave station side fault detection means detects the slave station fault occurrence, the slave station side control means for stopping the oscillation operation of the superimposed signal by the oscillating means in this slave station or stopping the light emission of the light emitting element. Therefore, the master station cannot detect the superimposed signal from the slave station, and can recognize the occurrence of a failure in the slave station.

That is, even if a failure occurs in the downstream optical transmission system, it is possible to specify this faulty slave station and issue an alarm.

An optical transmission system using this fault monitoring device is configured, for example, in a multi-drop topology or a star topology. In the former, an optical fiber between a master station and a plurality of slave stations is connected to a bus by an optical splitter. In this case, the master station and the individual slave stations are connected via optical splitters. The latter is an optical fiber connecting the master station and a plurality of slave stations in a radial manner.

As described above, in the optical transmission system employing the multi-drop topology or the star topology, the predetermined connection order corresponds to the order of slave stations sequentially connected from the master station.

Regarding the slave stations sequentially connected from the master station side, the light signal emitted by the light emitting element becomes closer to the master station regardless of the number of slave stations in the system configuration. It is desirable to be stable.

Further, in the multi-drop topology and the star topology, it is desirable to reduce optical beat noise generated by interference of optical signals from a plurality of slave stations. In general, by adding a superimposed signal to a light emitting element, the stability of an optical signal can be increased. However, it is known that the effect is greater when the frequency of the superimposed signal is lower.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the master station connects to each of the slave stations in a predetermined connection order. The frequency related to the superimposed signal of each slave station is characterized by increasing the frequency from the slave station farthest from the master station based on the connection order.

Therefore, according to the fault monitoring apparatus of the third aspect of the present invention, the frequency of the superimposed signal of each slave station is increased from the slave station in the order farthest from the master station based on the predetermined connection order. As a result, the closer to the master station, the higher the stability of the optical signal in the slave station can be, and the more significant the optical beat noise can be.

According to a fourth aspect of the present invention, there is provided a fault monitoring apparatus according to the first or second aspect.
The frequency related to the superimposed signal of each slave station is lower than the RF main signal band.

According to a fifth aspect of the present invention, in addition to the configuration of the third aspect, the frequency relating to the superimposed signal of each slave station is lower than the RF main signal band. It is characterized.

Therefore, according to the fault monitoring device of the fourth or fifth aspect of the present invention, in addition to the effects of the fault monitoring device of the first, second, or third aspect, in addition to the effects of the frequency lower than the RF main signal band, Since the superimposed signal is frequency-multiplexed with the RF main signal, it is possible to reduce the influence of transmission characteristics deterioration due to the stable operation of the light emitting element and reflection in the transmission path.

According to a sixth aspect of the present invention, there is provided a fault monitoring apparatus according to the first or second aspect.
The frequency related to the superimposed signal of each slave station is determined by this superimposed signal and R
The frequency is selected so that secondary intermodulation distortion generated when frequency-multiplexing the F main signal is not generated in the RF main signal band.

According to a seventh aspect of the present invention, in addition to the configuration of the third aspect, the frequency related to the superimposed signal of each slave station is such that the superimposed signal and the RF main signal are frequency-converted. It is characterized in that the frequency is selected so that secondary intermodulation distortion generated when multiplexing does not occur in the RF main signal band.

Therefore, according to the fault monitoring device according to claim 6 or 7 of the present invention, in addition to the effects of the fault monitoring device according to claim 1, 2, or 3, the frequency related to the superimposed signal of each slave station is added. Is a frequency selected so that the secondary intermodulation distortion generated when the superimposed signal and the RF main signal are frequency-multiplexed is not generated within the RF main signal band. The second-order intermodulation distortion caused by the nature occurs in the RF main signal band, and this
A situation that affects the transmission characteristics of the main signal can be prevented.

The fault monitoring device according to claim 8 of the present invention has the configuration according to claim 1 or 2,
The frequency of the superimposed signal of each slave station is a frequency selected so that an integral multiple of the frequency does not fall within the superimposed signal band of another slave station.

According to a ninth aspect of the present invention, in the fault monitoring apparatus according to the third aspect, in addition to the configuration of the third aspect, the frequency of the superimposed signal of each slave station is such that an integral multiple of the frequency is equal to that of another slave station. The frequency is selected so as not to be in the superimposed signal band.

Therefore, according to the fault monitoring device according to claim 8 or 9 of the present invention, in addition to the effects described in claim 1, 2, or 3, the frequency of the superimposed signal of each slave station is Since the frequency is selected so that the integral multiple does not fall within the superimposed signal band of another slave station, the harmonic distortion generated by the nonlinearity of the transmission system does not hinder the detection of superimposed signal disappearance. In addition, it is possible to improve the alarm accuracy and prevent malfunction.

According to a tenth aspect of the present invention, in addition to the configuration of the first or second aspect, the frequency of the superimposed signal of each slave station is generated by a combination of a plurality of superimposed signals. The secondary intermodulation distortion or the third intermodulation distortion is a frequency selected so as not to occur in the superimposed signal band of another slave station.

In the fault monitoring apparatus according to claim 11 of the present invention, in addition to the configuration according to claim 3, the frequency of the superimposed signal of each slave station may be a secondary frequency generated by a combination of a plurality of superimposed signals. The frequency is selected so that intermodulation distortion or third-order intermodulation distortion does not occur in a superimposed signal band of another slave station.

Therefore, claim 10 or claim 1 of the present invention.
According to the fault monitoring device of the first aspect, in addition to the effect of the fault monitoring device of the first, second, or third aspect, the frequency of the superimposed signal of each slave station is a secondary frequency generated by a combination of a plurality of superimposed signals. Since the inter-modulation distortion or the third-order inter-modulation distortion is set to a frequency selected so as not to occur in another superimposed signal band, the second-order inter-modulation distortion or the third order inter-modulation distortion caused by the nonlinearity of the transmission system. Sub-intermodulation distortion does not hinder detection of superimposed signal disappearance, so that it is possible to improve alarm accuracy and prevent malfunction.

An optical transmission system according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the optical transmission system shown in the present embodiment.

The optical transmission system 1 shown in FIG. 1 has a single master station 10, a plurality of slave station groups 20A (20B) each having three slave stations 20, and a plurality of downstream optical splitters 21a (2
1b, 21c, 21d, and 21e) to the slave station 20 in a multi-drop topology to transmit an optical signal from the master station 10 to the slave station 20, and each slave station group 20A ( 20B), the upstream optical splitters 26a, 26
b (26d, 26e) to the slave stations 20 in each slave station group 20A (20B) in a multi-drop topology, and from the slave stations 20 in each slave station group 20A (20B) to the master station 1
0 has a plurality of upstream optical transmission lines 40 for transmitting an RF multiplex signal described later.

The slave station group 20A (20B) comprises a first slave station group 20A and a second slave station group 20B. The first slave station group 20A includes a first slave station 20a and a third slave station 20A. The second slave station group 20B includes a second slave station 20d, a fourth slave station 20e, and a sixth slave station 20f.

The upstream optical transmission line 40 is connected to the first slave station group 20.
A first slave station 20a, third slave station 20b, and fifth slave station 20 of A
c in a multi-drop topology, and a second slave station 20d, a fourth slave station 20e, and a sixth slave station 20f of the second slave station group 20B. And a second slave station group upstream optical transmission line 40B connected by a topology.

The RF multiplex signal corresponds to a signal obtained by multiplexing an optical signal emitted from the light emitting element of each slave station with a superimposed signal for identifying each slave station and an RF main signal. It is.

The first slave station 20a of the first slave station group 20A splits an optical signal from the master station 10 obtained through the downstream optical transmission line 30 at a split ratio of approximately 1/6. A downstream optical splitter 21a, a first O / E 23a that converts an optical signal split by the first downstream optical splitter 21a into an electric signal, and outputs the electric signal to a signal output terminal 22a; The first E / O 25a having a light emitting element that emits an optical signal according to an electric signal obtained from the terminal 24a is connected to the first slave station group upstream optical transmission path 40A, and the first E / O 25a is connected to the first E / O 25a.
A first optical combiner 26a for combining the O25a optical signal with a combining ratio of approximately 1/3.

The second slave station 20d of the second slave station group 20B transmits the optical signal obtained through the first down-link optical splitter 21a of the down-link optical transmission line 30 with a branching ratio of approximately 1/5. A second downstream optical splitter 21d that branches, and a second O / E2 that converts the optical signal branched by the second downstream optical splitter 21d into an electric signal and outputs the electric signal to a signal output terminal 22d.
3D and a second E / O 25 having a light emitting element that emits an optical signal in accordance with an electric signal obtained from the signal input terminal 24d.
d, connected to the second slave station group upstream optical transmission line 40B,
A second optical combiner 26d for combining the optical signal of the second E / O 25d at a combining ratio of approximately 1/3.

An optical signal obtained via the second downstream optical splitter 21d of the downstream optical transmission line 30 is transmitted to the third mobile station 20b of the first mobile station group 20A at a branching ratio of approximately 1/4. A third downstream optical splitter 21b that branches, and a third O / E2 that converts the optical signal branched by the third downstream optical splitter 21b into an electric signal and outputs the electric signal to a signal output terminal 22b.
3E and a third E / O 25 having a light emitting element that emits an optical signal in accordance with an electric signal obtained from the signal input terminal 24b.
b and the first slave station group upstream optical transmission line 40A,
A third optical combiner 26b for combining the optical signal of the third E / O 25b at a combining ratio of approximately 1/2.

The fourth slave station 20e of the second slave station group 20B transmits an optical signal obtained through the third downstream optical splitter 21b of the downstream optical transmission line 30 with a branching ratio of approximately 1/3. A fourth downstream optical splitter 21e that branches, and a fourth O / E2 that converts the optical signal branched by the fourth downstream optical splitter 21e into an electric signal and outputs the electric signal to a signal output terminal 22e.
3E and a fourth E / O 25 having a light emitting element that emits an optical signal in response to an electric signal obtained from the signal input terminal 24e.
e and the second slave station group upstream optical transmission path 40B,
A fourth optical combiner 26e for combining the optical signal of the fourth E / O 25e at a combining ratio of approximately 1/2.

The fifth sub-station 20c of the first sub-station group 20A transmits the optical signal obtained through the fourth down-link optical branching unit 21e of the down-link optical transmission line 30 with an almost 1/2 splitting ratio. A fifth downstream optical splitter 21c that branches, and a fifth O / E2 that converts the optical signal branched by the fifth downstream optical splitter 21c into an electric signal and outputs the electric signal to a signal output terminal 22c.
3c, and a light emitting element that emits an optical signal in accordance with an electric signal obtained from the signal input terminal 24c. The light emitting element is connected to the first slave station group upstream optical transmission line 40A to emit an optical signal by the light emitting element. 5E / O25c.

The sixth slave station 20f of the second slave station group 20A converts the optical signal obtained through the fifth downstream optical splitter 21c of the downstream optical transmission line 30 into an electric signal, and A sixth O / E 23f that outputs a signal to the signal output terminal 22c;
A light emitting element that emits an optical signal in response to an electric signal obtained from the signal input terminal 24f, and is connected to the second slave station group upstream optical transmission path 40B to emit an optical signal from the light emitting element; / O25f.

Since the master station 10 and the slave stations 20a, 20b, 20c are connected in a multi-drop topology in the first slave station group upstream optical transmission line 40A, the first slave station group 20c The optical signal from the 5E / O25c and the third
The third optical combiner 26b combines the optical signal from the third E / O 25b of the slave station 20b with an approximately 1: 1 combining ratio, and combines the optical signal combined by the third upstream optical combiner 26b with the optical signal. And the optical signal from the first E / O 25a of the first slave station 20a is combined by the first optical combiner 26a at a combining ratio of approximately 2: 1 and the optical signal combined by the first optical combiner 26a is This is transmitted to the first slave station group O / E 13A of the master station 10.

The second slave station group upstream optical transmission line 40B
, The master station 10 and each of the slave stations 20d, 20e, 20f
And are connected in a multi-drop topology,
The optical signal from the sixth E / O 25f of the sixth slave station 20f and the optical signal from the fourth E / O 25e of the fourth slave station 20e are converted into a fourth signal.
The optical combiner 26e combines the optical signals at a combining ratio of approximately 1: 1 and combines the optical signal combined by the fourth optical combiner 26e with the optical signal from the second E / O 25d of the second slave station 20d. The two light combiners 26d combine the lights at a combining ratio of about 2: 1 and transmit the optical signal combined by the second light combiner 26d to the second slave station group O / E13B.

Further, the first slave station 2 of the first slave station group 20A.
0a, the third slave station 20b, and the fifth slave station 20c have light emitting elements having different emission wavelengths, respectively. The first slave station 20a has the light emitting element LD-B, and the third slave station 20b has the light emitting element LD-. C
The fifth slave station 20c has a light emitting element LD-A. The interval of the emission wavelength band of each slave station in the same group is determined in consideration of the spectral line width, the change of the emission wavelength due to the change of the ambient temperature and the bias current, the required specification value such as the CNR of the system, and the transmission signal band. Is what you do.

The second slave station 2 of the second slave station group 20B
0d, the fourth slave station 20e, and the sixth slave station 20f also have light emitting elements having different emission wavelengths, the second slave station 20d has a light emitting element LD-B, and the fourth slave station 20e has a light emitting element LD-. C
The sixth slave station 20f has a light emitting element LD-A.

That is, the first slave station 20a of the first slave station group 20A and the second slave station 20d of the second slave station group 20B include the first and second optical combiners 26a and 26d in the upstream optical transmission system. The third slave station 20b and the fourth slave station 20e have the same part related to the upstream optical transmission system including the third and fourth optical combiners 26b and 26e.
0c and the sixth slave station 20f have the same portion related to the upstream optical transmission system.

Also, at least the master station 1 connected via the first slave station group upstream optical transmission line 40A in the first slave station group 20A.
0 and slave stations 20a, or two slave stations 20a and slave stations 20b
The combination between (20b and 20c) is the second slave station group 20
It is the same as the combination between at least the master station 10 and the slave station 20d or between the two slave stations 20d and the slave stations 20e (20e and 20f) connected via the second slave station group upstream optical transmission line 40B in B. .

Next, the details of the fault monitoring device which is the main feature of the present invention will be described. FIG. 2 is a block diagram showing a schematic configuration inside the failure monitoring device between the master station 10 and the slave station 20a in the optical transmission system 1 according to the present embodiment.

In FIG. 2, slave station 2 in first slave station group 20A
0a is the first down-link optical branching device 21a, the first O / E 23a, the first up-link optical branching device 26a and the 1E
An oscillator circuit 27a (27) that oscillates a superimposed signal of a predetermined frequency preset for each slave station in addition to / O25a;
The level of the optical signal branched by the first down-link optical splitter 21a is detected, and based on the detection result, the down-link optical transmission path 30
And a control unit 29 for controlling the light emission operation of the first E / O 25a or the oscillation operation of the oscillation circuit 27a based on the result of the detection of the failure.
a (29), a synthesizer 28a (28) for multiplexing the superimposed signal and the RF main signal oscillated by the oscillation circuit 27a to generate an RF multiplexed signal, and the above-described RF multiplexed signal to an optical signal. And a first E / O 25a for conversion.

Incidentally, the first slave station group 20 of this optical transmission system
In each of the slave stations 20 in A or the second slave station group 20B,
Based on the connection order between the slave station 20 and the master station 10 in each of the slave station groups 20A and 20B, the frequency of the superimposed signal is set to decrease as the slave station 20 approaches the master station 10. is there. That is, in the first slave station group 20A, the frequency of the superimposed signal at the first slave station 20a is f1, the frequency of the superimposed signal at the third slave station 20b is f2, and the frequency of the superimposed signal at the fifth slave station 20c is f3. In this case, f1 <f2 <f
Condition 3 is satisfied.

In FIG. 2, only the first slave station 20a in the first slave station group 20A has been described as an example.
0 has the same configuration.

In FIG. 2, the first slave station group O / E of the master station 10 is shown.
13A is a master station O / E32 for converting an optical signal of the first slave station group 20A into an electric signal, and superimposing the RF multiplexed signal of the first slave station group 20A on the RF main signal and the first slave station group 20A. And a demultiplexer 31 for demultiplexing the signal and a signal. Here, the first
The optical signal of the slave station group 20A is an optical signal obtained by combining the optical signals from the first slave station 20a, the third slave station 20b, and the fifth slave station 20c by the first optical combiner 26a and the third optical combiner 26b. Similarly, the superimposed signal of the first slave station group 20A refers to the optical signals from the first slave station 20a, the third slave station 20b, and the fifth slave station 20c, and the first optical combiner 26a. And third
This corresponds to the superimposed signal synthesized by the optical synthesizer 26b.

Further, the master station 10 includes the duplexer 3
A plurality of BPs for extracting a superimposed signal (predetermined frequency) for each slave station from the superimposed signal in the first slave station group 20A demultiplexed at 1
F16, a level detector 17 for detecting the level of the superimposed signal for each slave station obtained by the BPF 16, and the presence / absence of a failure of the superimposed signal based on the level result of each superimposed signal by the level detector 17. And a controller 1 for determining, based on the result of the failure determination, the failure of the slave station 20 corresponding to the superimposed signal related to the result of the failure determination.
9 and an alarm generator 18 for turning on an alarm LED corresponding to each slave station 20 when it is determined that there is a failure.

The BPF 16 and the level detector 17
Each of the numbers corresponds to the number of slave stations in the slave station group,
For example, the BPF 16a extracts a superimposed signal f1 included in the RF multiplex signal from the first slave station 20a,
The BPF 16b extracts the superimposed signal f2 included in the RF multiplex signal from the third slave station 20b.
c extracts the superimposed signal f3 included in the RF multiplex signal from the fifth slave station 20c.

The control section 19 includes the level detection section 17
The presence or absence of a superimposed signal is determined based on the level result of the superimposed signal, and the presence / absence of a failure of the slave station corresponding to the superimposed signal related to the result of the determination is determined based on the result of the determination.

In FIG. 2, the first slave station group O / E13
Although the description has been made by taking only A as an example, the second slave station group O / E13B
Has the same configuration.

Next, the operation of the optical transmission system 1 according to the present embodiment will be described.

The fifth slave station 20c of the first slave station group 20A receives the RF main signal obtained from the signal input terminal 24c and the oscillation circuit 2
The RF multiplexed signal is multiplexed with the superimposed signal f3 from the seventh unit 7 by the combiner 28, the RF multiplexed signal is converted into an optical signal by the fifth E / O 25c, and transmitted to the third optical combiner 26b of the third slave station 20b.

The third slave station 20b receives the RF main signal obtained from the signal input terminal 24b and the superimposed signal f from the oscillation circuit 27.
2 are multiplexed by the combiner 28, the RF multiplexed signal is converted into an optical signal by the third E / O 25b, and transmitted to the third optical combiner 26b.

The third optical combiner 26b combines the optical signal of the fifth slave station 20c and the optical signal of the third slave station 20b at a combining ratio of approximately 1: 1 and combines the combined optical signal with the first optical signal. Photosynthesizer 2
6a.

The first slave station 20a multiplexes the RF main signal obtained from the signal input terminal 24a and the superimposed signal f1 from the oscillation circuit 27a in a combiner 28a, and transfers the RF multiplexed signal to a first E / O 25a. The optical signal is converted to an optical signal and transmitted to the first optical combiner 26a.

The first light combiner 26a is connected to the third light combiner 26.
The optical signal combined in b and the optical signal of the first slave station 20a are combined at a combining ratio of approximately 2: 1 and the combined second optical signal is transmitted via the first slave station group upstream optical transmission line 40A. The optical signal of one slave station group 20A is transmitted to the first slave station group O / E 23a of the master station 10.

In the first slave station group O / E13A,
The master station O / E 32 converts the optical signal of the first slave station 20A into an electric signal, and the splitter 31 outputs the RF main signal of the first slave station group 20A and the superimposed signal of the first slave station group 20A. Then, the RF main signal of the first slave station group 20A is transmitted to the output unit 14, and the superimposed signal of the first slave station group 20A is transmitted to each BPF 16.

The master station O / E 32 communicates with the first slave station group 2
The optical signal of 0A is converted into an electric signal, and this electric signal is supplied to one input of the synthesizing circuit 15.

The sixth slave station 20f of the second slave station group 20B
Multiplexes the RF main signal obtained from the signal input terminal 24f and the superimposed signal from the oscillation circuit 27 in the synthesizer 28,
The RF multiplexed signal is converted into an optical signal by the sixth E / O 25f and transmitted to the fourth optical combiner 26e of the fourth slave station 20e.

The fourth slave station 20e multiplexes the RF main signal obtained from the signal input terminal 24e and the superimposed signal from the oscillation circuit 27 in the synthesizer 28, and multiplexes the RF multiplexed signal into the fourth E signal.
The signal is converted into an optical signal by / O25e and transmitted to the fourth optical combiner 26e.

The fourth optical combiner 26e combines the optical signal of the sixth slave station 20f and the optical signal of the fourth slave station 20e at a combining ratio of approximately 1: 1 and combines the combined RF multiplexed signal with the fourth combined signal. The light is transmitted to the two-light combiner 26d.

The second slave station 20d multiplexes the RF main signal obtained from the signal input terminal 24d and the superimposed signal from the oscillation circuit 27 in the synthesizer 28, and multiplexes the RF multiplexed signal into the second E / O.
The signal is converted into an optical signal at 25d and transmitted to the second optical combiner 26d.

The second light combiner 26d is connected to the fourth light combiner 26.
e, and the optical signal of the second slave station 20b are combined at a combining ratio of approximately 2: 1 and the combined signal is transmitted via the second slave station group upstream optical transmission line 40B. Second child station group 20
The optical signal of B is transmitted to the second slave station group O / E13B of the master station 10.

In the second slave station group O / E13B,
The optical signal in the second slave station group 20B is transmitted to a master station O / E (not shown).
, And converts the RF multiplexed signal of the second slave station group 20B by a duplexer (not shown) into the RF main signal in the second slave station group 20B, similarly to the first slave station group O / E 13A. Signal and second slave station group 2
The signal is demultiplexed into a superimposed signal in 0B and the superimposed signal in the second slave station group 20B is transmitted to each BPF (not shown).

The master station O / E is connected to the second slave station group 20B.
Is converted into an electric signal, and this electric signal is supplied to the other input of the synthesizing circuit 15.

The synthesizing circuit 15 is provided with the first slave station group O /
The electric signals from E13A and the second slave station group O / E13B are combined and output to the signal output terminal 14.

Here, the operation when a failure occurs in the first slave station 20a in the first slave station group upstream optical transmission line 40A in the first slave station group 20A will be described.

As described above, the synthesizer 28a synthesizes the external electric signal and the superimposed signal of the frequency band for identifying the own station 20a emitted from the oscillation circuit 27a to generate the RF multiplexed signal. The RF multiplexed signal is converted into an optical signal by the first E / O 25a of the first slave station 20a. This optical signal and the optical signal combined by the third optical combiner 26b are combined via the first optical combiner 26a, and the first
The data is transmitted to the slave station group O / E 13A.

The duplexer 31 of the first slave station group O / E 13A
Converts the optical signal of the first slave station group 20A into the first slave station group 20A.
A into an optical signal of A and a superimposed signal of the first slave station group 20A.
The superimposed signal in the first slave station group 20A is transmitted to the BPF 16 (16
a, 16b, 16c).

Each of the BPFs 16 includes superimposed signals f1, f2, f3 of a predetermined frequency band, that is, the first slave station 20a,
The superimposed signals of the third slave station 20b and the fifth slave station 20c are respectively extracted, and the superimposed signals are extracted by the level detector 17 (17a, 17a,
17b, 17c). The level detector 17 detects the level of each superimposed signal and transmits the level result to the controller 19.

The control unit 19 determines the presence / absence of a failure in the slave station of the superimposed signal based on the level result, detects the occurrence of a failure in each slave station based on the determination result, and determines the failure of the slave station. Based on the result, the display of the relevant slave station and the alarm generator 18 are controlled.

Therefore, the control unit 19 determines that there is no level of the superimposed signal f1 from the level detection unit 17a (the superimposed signal disappears).
Is received, it is determined that a failure has occurred in the first child station 20a corresponding to the superimposed signal f1, and the first
The alarm generator 18 turns on an alarm LED for notifying that a failure has occurred in the slave station 20a.

Next, an operation when a failure occurs in the first slave station 20a in the first slave station group 20A on the downstream optical transmission line 30 will be described.

An optical signal is transmitted from the master station 10 via the downstream optical transmission line 30 to the first slave station 20a.
When the controller 29a determines that the level of the optical signal is lower than normal, the first E / O 25a in the first slave station 20a
Or the oscillation operation of the superimposed signal of the oscillation circuit 27a is stopped.

As described above, the control unit 19 on the master station 10 side
Is the first slave station 20a added to the RF multiplexed signal of the first slave station group 20A.
Is obtained, the first slave station 20a is determined to have a failure, and the first slave station 20a is determined to have a fault.
Alarm LE for notifying that a failure has occurred in the slave station 20a
D is turned on by the alarm generator 18. It should be noted that the slave station failure is notified by the lighting display of the alarm LED,
The notification may be made by an alarm sound.

According to the present embodiment, an optical signal (RF multiplexed signal) is transmitted from the slave station 20 to the master station 10, such as a failure in the upstream optical transmission line, a failure in the slave station power supply or a failure in the slave station light emitting element. Even if a failure that cannot be transmitted, that is, a failure occurs in the upstream optical transmission line system, the master station 10 extracts a superimposed signal from the RF multiplexed signal including the RF main signal from each slave station 20, Based on the extracted superimposed signal, the presence of a slave station failure is detected, and the fact that a failure has occurred in the slave station 20 corresponding to the superimposed signal is output by the alarm generator 18. It is possible to perform the detection without fail, and without providing a complicated circuit and communication control means on the master station 10 side, and without having to constantly monitor the state of the slave station by complicated two-way communication control. Multiple slave stations 20 in system 1
Can identify the disabled child station.

Also, according to the present embodiment, the downstream optical transmission from the master station 10 to the slave station 20 does not directly cause the slave station to stop emitting light, such as a break in the downstream optical transmission path or a failure in the slave station light-receiving element. Even if a failure occurs in the system, the oscillation operation of the superimposed signal by the oscillation circuit 27 of the slave station 20 relating to the failure or the E / O 25a (25b, 25c, 25
d, 25e, and 25f), the light emitting operation is stopped, so that the master station 10 cannot detect the superimposed signal from the slave station 20, and determines that there is a slave station failure and recognizes the faulty slave station. can do.

According to the present embodiment, each slave station 20
Since the frequency of the superimposed signal is increased from the slave station 20 in the order farthest from the master station 10 based on the predetermined connection order,
The closer to the master station 10, the higher the stability of the optical signal in the slave station 20 and the more the optical beat noise can be reduced.

Further, according to the present embodiment, a superimposed signal having a frequency lower than the RF main signal band is frequency-multiplexed to the RF main signal, so that the operation of the light emitting element can be stabilized and the reflection in the transmission line can be reduced. This can reduce the influence of transmission characteristic degradation caused by the transmission.

According to the present embodiment, each slave station 20
The frequency related to the superimposed signal oscillated by the oscillation circuit 27 is selected so that secondary intermodulation distortion generated when the superimposed signal and the RF main signal are multiplexed does not occur in the RF main signal band. Frequency, the secondary intermodulation distortion caused by the non-linearity of the transmission system occurs in the RF main signal band, thereby affecting the transmission characteristics of the RF main signal. Can be prevented.

The frequency of the superimposed signal oscillated by the oscillation circuit 27 in each slave station 20 is a frequency selected so that an integral multiple of the frequency does not fall within the superimposed signal band of another slave station. In this case, it is possible to improve the alarm accuracy and prevent malfunctions so that harmonic distortion generated by nonlinearity of the transmission system does not hinder detection of superimposed signal disappearance.

Also, the frequency of the superimposed signal oscillated by the oscillation circuit 27 in each slave station 20 is changed by the second or third order intermodulation distortion generated by a combination of a plurality of superimposed signals. When the frequency is selected so as not to be generated in the band, the secondary intermodulation distortion or the tertiary intermodulation distortion caused by the nonlinearity of the transmission system does not hinder the detection of superimposed signal disappearance. Thus, it is possible to improve the alarm accuracy and prevent malfunction.

[0101]

According to the fault monitoring apparatus of the present invention configured as described above, the master station extracts the superimposed signal from the RF multiplex signal including the RF main signal from each slave station, and extracts the superimposed signal. When the occurrence of a slave station failure is detected based on the disappearance, the failure notification means is notified by the failure notification means that a failure has occurred in the slave station corresponding to the lost superimposed signal. Can be implemented reliably,
Without providing a complicated circuit and communication control means on the master station side, and without always monitoring the status of the slave station with complicated two-way communication control, a faulty slave station can be detected from a plurality of slave stations in the optical transmission system. Can be identified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration inside an optical transmission system shown in the present embodiment.

FIG. 2 is a block diagram illustrating details inside a fault monitoring device of the optical transmission system according to the present embodiment.

[Explanation of symbols]

Reference Signs List 1 optical transmission system 10 master station 12 master station E / O (light emitting element) 13A first slave station group O / E (light receiving element) 13B second slave station group O / E (light receiving element) 16 BPF (signal extraction means) Reference Signs List 17 Level detection unit (failure detection means) 18 Alarm generator (failure notification means) 19 Control unit (failure detection means) 20 Slave station 20A First slave station group 20B Second slave station group 23a First O / E (child) 23b Second O / E (slave station light receiving element) 23c Third O / E (slave station light receiving element) 23d Fourth O / E (slave station light receiving element) 23e Fifth O / E (slave station side) 23f 6th O / E (slave station light receiving element) 25a 1st E / O (slave station light emitting element) 25b 2nd E / O (slave station light emitting element) 25c Third E / O (slave station light emitting element) 25d 4th E / O (slave station side light emitting element) 25e 5th E / O Slave side light emitting element) 25f Sixth E / O (slave side light emitting element) 27 (27a) Oscillator circuit (oscillating means) 28 (28a) Synthesizer (RF combining means) 29 (29a) Control unit (slave station side failure) Detection means, slave station side control means) 30 downstream optical transmission line (optical transmission line) 31 demultiplexer 40 upstream optical transmission line (optical transmission line)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Susumu Tsubosaka 4-3-1 Tsunashimahigashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture Inside Matsushita Communication Industrial Co., Ltd. (72) Kazuko Funakura Tsunashima-higashi, Kohoku-ku, Yokohama-shi, Kanagawa 4-3-1, Matsushita Communication Industrial Co., Ltd. (72) Inventor Masanori Ieki 216-18 Motojocho, Hamamatsu-shi, Shizuoka Prefecture Matsushita Communication Shizuoka Research Laboratory Co., Ltd. (72) Inventor Kazuhiro Uchiyama Hamamatsu-shi, Shizuoka Prefecture 216-18 Motojocho Matsushita Communication Shizuoka Research Laboratories Co., Ltd. (72) Inventor Yoshio Ebine 2-10-1, Toranomon, Minato-ku, Tokyo NTT Mobile Communications Network Co., Ltd. (72) Inventor Yu Fukuya 2-10-1 Toranomon, Minato-ku, Tokyo NTT Mobile Communications Network Co., Ltd.

Claims (11)

[Claims] An optical transmission system having a master station, a plurality of slave stations, and an optical transmission line connected between the master station and the slave station and optically transmitting an RF main signal between the master station and the slave station. A fault monitoring device for monitoring a fault of a slave station in a master station, the slave station oscillating means for oscillating a superimposed signal having a different frequency for each slave station, and an RF main unit to be transmitted from the slave station. An RF synthesizing unit that frequency-multiplexes the signal and the superimposed signal by the oscillation unit to generate an RF multiplexed signal; and a light emitting element that converts the RF multiplexed signal into an optical signal and transmits the optical signal. An optical signal transmitted through the optical transmission path is received, and a light receiving element for photoelectrically converting the optical signal is obtained.
A signal extracting means for extracting the F main signal and a superimposed signal for each slave station; and a fault detecting a fault occurrence in the slave station based on the superimposed signal disappearance for each slave station extracted by the signal extracting means. Presence / absence detection means, failure notification means for reporting that a failure has occurred for each slave station, and when the failure presence / absence detection means detects failure occurrence in the slave station based on the disappearance of the superimposed signal, Control means for controlling the fault notifying means so as to notify that a fault has occurred in a slave station corresponding to the signal. A slave station for receiving an optical signal from the master station via an optical transmission line; and a slave station based on the optical signal received by the slave station. And a slave station side fault detecting means for detecting the occurrence of a fault in the optical transmission line. When the slave station side fault detecting means detects the occurrence of a slave station fault, the oscillation operation of the superimposed signal by the oscillating means in the slave station is stopped. 2. The fault monitoring device according to claim 1, further comprising a slave-station-side control unit for causing the light-emitting element to stop emitting light. 3. The master station connects to each of the slave stations in a predetermined connection order, and the frequency associated with the superimposed signal of each slave station is determined based on the connection order from the slave station in the order farthest from the master station. 3. The fault monitoring device according to claim 1, wherein the frequency is increased. 4. The frequency associated with the superimposed signal of each slave station is R
3. The fault monitoring device according to claim 1, wherein the frequency is lower than the F main signal band. 5. The frequency related to the superimposed signal of each slave station is R
4. The fault monitoring device according to claim 3, wherein the frequency is lower than the frequency of the F main signal band. 6. The frequency associated with the superimposed signal of each slave station is selected such that secondary intermodulation distortion generated when the superimposed signal and the RF main signal are frequency-multiplexed does not occur in the RF main signal band. 2. The frequency of the input signal
Or the fault monitoring device according to 2. 7. The frequency associated with the superimposed signal of each slave station is selected such that secondary intermodulation distortion generated when the superimposed signal and the RF main signal are frequency-multiplexed does not occur in the RF main signal band. 4. The frequency according to claim 3, wherein
The fault monitoring device as described. 8. The frequency of a superimposed signal of each slave station is a frequency selected such that an integral multiple of the frequency does not fall within the superimposed signal band of another slave station.
Or the fault monitoring device according to 2. 9. The frequency of the superimposed signal of each slave station is a frequency selected so that an integral multiple of the frequency does not fall within the superimposed signal band of another slave station.
The fault monitoring device as described. 10. The frequency of the superimposed signal of each slave station is such that secondary intermodulation distortion or tertiary intermodulation distortion caused by a combination of a plurality of superimposed signals does not occur in the superimposed signal band of another slave station. The fault monitoring device according to claim 1 or 2, wherein the frequency is selected. 11. The frequency of the superimposed signal of each slave station is such that secondary intermodulation distortion or tertiary intermodulation distortion generated by a combination of a plurality of superimposed signals does not occur in the superimposed signal band of another slave station. 4. The fault monitoring device according to claim 3, wherein the frequency is selected from the following.